IMF First Deputy Managing Director David Lipton told the BBC World Service the tradition by which a European heads the fund while an American leads the World Bank was coming under pressure and the next appointment would be "strictly merit-based".
Described on the same radio program as an "incredible anachronism" by former IMF Chief Economist Kenneth Rogoff, the convention that has ensured that Europeans lead the fund has been increasingly challenged during the euro zone crisis.
Lipton said that when Lagarde steps down, her successor would probably come from a non-European country.
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"With candidates coming forward from around the world, I think it's much more likely the next time around than it has ever been," he said.
"There are more and more eminently qualified people from outside Europe and the United States and I think the fact that there's been so much focus on crisis in the United States right at the early stages of the global financial crisis and with Europe, is going to lead to a sense that there has to be a broader pool for the leadership role," Lipton said.
Lagarde, a former French finance minister, took over as head of the IMF in 2011 after her predecessor, Dominique Strauss-Kahn was forced to resign over a sex scandal.
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Her five-year term comes to an end next year but she was quoted last month as saying she would consider a second term if she had the support of the IMF's members.
Although there is no formal requirement that the leader of the IMF come from Europe, it has been the practice ever since the institution was set up after World War Two, while the World Bank has always been led by an American.
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